Field of the Invention
The present invention relates to a lens apparatus, and particularly to a lens apparatus for use in television photographing, cinematography, and the like, including an endless operating unit, and to an image pickup apparatus including the lens apparatus.
Description of the Related Art
It is generally known that a television lens (hereinafter referred to as a lens apparatus) for use in television photographing operates a driving target such as a stop (hereinafter referred to as an iris), a zoom lens, or a focus lens, based on an instruction from a camera connected to the lens by using various operating apparatuses.
An operating apparatus illustrated in FIG. 9 is connected to a lens apparatus for communication and transmits position information in accordance with a rotation position of an operating unit 901 to the lens apparatus as an instructed position, thereby enabling control of the position of a driving target of the lens apparatus.
The operating apparatus includes a non-endless operating apparatus in which an operating unit has a limited rotation angle range and an endless operating apparatus in which an operating unit has a non-limited rotation angle range. In the case of the non-endless operating apparatus, position information proportional to the rotation position of the operating unit is used as an instructed position. Thus, when an operation right is switched to the operating apparatus from another operation source such as a camera, if the position of the driving target at this time does not correspond to the rotation position of the operating unit, the driving target moves to a position corresponding to the rotation position of the operating unit disadvantageously. For example, when the operation right is switched to an operating apparatus after the focus lens has been driven by using an autofocus function, a problem such as unintentional driving of the focus lens based on an instruction from the operating apparatus arises. In view of this, it is necessary to prevent lens driving that is not intended by a user in switching the operation right.
In a manner similar to the endless operating apparatus, for a conventional lens apparatus constituting an endless operating unit providing non-limited rotation, a technique for preventing lens driving that is not intended by a user in switching an operation right was disclosed.
For example, Japanese Patent No. 3777502 discloses a technique (hereinafter referred to as a matching technique) of matching a position of an endless operating unit with a lens position by using a final control value to be output to a driving unit (hereinafter referred to as a final control value) when an operation right is switched to an endless operating unit.
This technique will be described in detail below. First, a lens apparatus stores an instructed position (hereinafter referred to as an input control value) from an endless operating unit, and the value to be stored is updated upon the input control value changing. If the operation right is switched to the endless operating unit, a difference value between the final control value before switching of the operation right and the input control value is calculated from Equation (1):difference value=final control value (before switching)−input control value  (1)
A final control value after switching of the operation right is calculated from Equation (2):final control value (after switching)=input control value+difference value  (2)
Equation (1) and Equation (2) show that the final control value is uniform before and after switching the operation right.
In other words, the final control value before switching of the operation right is at a position at which matching is obtained (hereinafter referred to as a matching position), and matching is performed between the endless operating unit and the lens position by using the difference value. That is, unless neither the position of the endless operating unit nor the lens position changes between before and after switching of the operation right, movement of the lens position independent of operation of the endless operating unit does not occur in switching the operation right.
FIG. 10A shows a relationship between the input control value and the final control value in a case where the operation right is switched to the endless operating unit at time T. In the case where the operation right is switched to the endless operating unit, the position of the lens apparatus and the position of the endless operating unit are matched so that unintentional lens driving can be prevented in switching the operation right.
In the known technique disclosed in Japanese Patent No. 3777502 described above, however, the lens is unintentionally driven when a final control value is calculated by correcting an input control value for the purpose of operation except matching. For example, in the case of calculating a final control value from Equation (3):final control value (before switching)=input control value (before switching)+correction value α  (3)
the difference value described above can be obtained from Equation (4):difference value=final control value (before switching)−correction value α−input control value  (4)
The obtained difference value is substituted into Equation (2), and a final control value after switching the operation right is obtained from Equation (5):final control value (after switching)=final control value (before switching)−correction value α  (5)
As shown in the above description, a difference corresponding to the correction value α occurs in the final control value before and after switching of the operation right.
FIG. 10B shows a relationship between the input control value and the final control value in a case where the operation right is switched to the endless operating unit at time T in calculating the final control value from Equation (3). In the case of calculating the final control value by correcting the input control value, if a position at which matching is obtained (hereinafter referred to as a matching position) is defined as the final control value, the lens is unintentionally driven to a degree corresponding to the correction value α only by switching the operation right.
As described above, in the known technique described above, the case of calculating the final control value by correcting the input control value has a problem in which merely switching the operation right causes a lens driving that is not intended by a user. In the case of using the endless operating apparatus described above, a similar problem arises.
In a correction process of calculating the final control value by performing correction, whether the correction process is performed or not depends on conditions of the lens apparatus, and thus, merely performing addition or subtraction of the correction value causes a problem of unintentional movement of the lens.